B3.3 Muscle and Motility
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example of motile organism
bacteria
sessile organism example
Sponges, corals and anemones Most fungi species All plant species
what does each striated muscle fibre contain
organised arrangement of contractile proteins in the cytoplasm Many nuclei sarcoplasmic reticulum (SR) which stores calcium and conveys signals to all parts of the fibre at once using protein pumps in the membranes
what are myofibrils
bundles of actin and myosin filaments, which slide past each other during muscle contraction
when a muscle contacts what happens
the sarcomere shortens due to the sliding of actin and myosin filaments
simplified sliding filament model
myosin head binds to exposed binding site on actin molecule myosin head moves by rowing action ATP binds to myosin head so it separates from actin filament, ATP is now hydrolysed so moves myosin back to original position cycle is repeated at a binding site further along actin molecule, closer to z disc
antagonistic muscle action
A muscle pulls in one direction at a joint and the other muscle pulls in the opposite direction
what is an isometric contraction
a muscle contraction without motion
what protein does muscle contraction and relaxation rely on
titin
what is titin
a large protein that joins the ends of the myosin filaments to the z-line it has many folds which give it spring like properties for contraction
what happens when a muscle is relaxed
sarcomere lengthens and the titin is stretched out
when does a skeletal muscle contract
when it receives an impulse from a motor neurone via the neuromuscular junction
what does a motor unit of a skeletal muscle consist of
motor neurone, muscle fibres, neuromuscular junctions
what polysaccharides made up exoskeletons
chitin
how are synovial joints chracterised
by a joint cavity filled with a lubricating synovial fluid which reduces friction which is produced by synovial membrane
example of an antagonistic muscle pair
intercostal muscles
intercostal muscles in ribcage
External intercostal muscles, pull the rib cage up(increases volume of thorax- air drawn in by decrease in air pressure) Internal intercostal muscles pull the ribcage down
what measures range of movements in joints
goniometer
what is locomotion
the ability to move from one place to another
example of locomotion
Guinea pigs Foraging for food Caribou dear Migration